#include <asm.h>
#include <csr.h>

.macro SAVE_CONTEXT
  .local _restore_kernel_tpsp
  .local _save_context
  /*
   * If coming from userspace, preserve the user thread pointer and load
   * the kernel thread pointer.  If we came from the kernel, sscratch
   * will contain 0, and we should continue on the current TP.
   */
  csrrw tp, CSR_SSCRATCH, tp
  bnez tp, _save_context

_restore_kernel_tpsp:
  csrr tp, CSR_SSCRATCH
  sd sp, PCB_KERNEL_SP(tp)
_save_context:
  sd sp, PCB_USER_SP(tp)
  ld sp, PCB_KERNEL_SP(tp)
  addi sp, sp, -(OFFSET_SIZE)

  /* TODO: save all general purpose registers here! */
  sd sp, PCB_KERNEL_SP(tp)
  sd ra, OFFSET_REG_RA(sp)    
  sd gp, OFFSET_REG_GP(sp)
  sd tp, OFFSET_REG_TP(sp)
  sd t0, OFFSET_REG_T0(sp)
  sd t1, OFFSET_REG_T1(sp)
  sd t2, OFFSET_REG_T2(sp)
  sd s0, OFFSET_REG_S0(sp)
  sd s1, OFFSET_REG_S1(sp)
  sd a0, OFFSET_REG_A0(sp)
  sd a1, OFFSET_REG_A1(sp)
  sd a2, OFFSET_REG_A2(sp)
  sd a3, OFFSET_REG_A3(sp)
  sd a4, OFFSET_REG_A4(sp)
  sd a5, OFFSET_REG_A5(sp)
  sd a6, OFFSET_REG_A6(sp)
  sd a7, OFFSET_REG_A7(sp)
  sd s2, OFFSET_REG_S2(sp)
  sd s3, OFFSET_REG_S3(sp)
  sd s4, OFFSET_REG_S4(sp)
  sd s5, OFFSET_REG_S5(sp)
  sd s6, OFFSET_REG_S6(sp)
  sd s7, OFFSET_REG_S7(sp)
  sd s8, OFFSET_REG_S8(sp)
  sd s9, OFFSET_REG_S9(sp)
  sd s10, OFFSET_REG_S10(sp)
  sd s11, OFFSET_REG_S11(sp)
  sd t3, OFFSET_REG_T3(sp)
  sd t4, OFFSET_REG_T4(sp)
  sd t5, OFFSET_REG_T5(sp)
  sd t6, OFFSET_REG_T6(sp)
  /*
   * Disable user-mode memory access as it should only be set in the
   * actual user copy routines.
   *
   * Disable the FPU to detect illegal usage of floating point in kernel
   * space.
   */

  /* TODO: save sstatus, sepc, stval, scause and sscratch on user stack */
  ld s0, PCB_USER_SP(tp)
  li s1, SR_SUM | SR_FS
  csrr s1 ,CSR_SSTATUS
  csrr s2, CSR_SEPC
  csrr s3, CSR_STVAL
  csrr s4, CSR_SCAUSE
  csrr s5, CSR_SSCRATCH
  sd s0, OFFSET_REG_SP(sp)
  sd s1, OFFSET_REG_SSTATUS(sp)
  sd s2, OFFSET_REG_SEPC(sp)
  sd s3, OFFSET_REG_SBADADDR(sp)
  sd s4, OFFSET_REG_SCAUSE(sp)
  sd s5, OFFSET_REG_TP(sp)
.endm

.macro RESTORE_CONTEXT
  /* TODO: Restore all registers and sepc,sstatus */
  sd sp, PCB_KERNEL_SP(tp)
  ld tp, current_running

  la t0, kernel_lock
  sd x0, (t0)

  ld sp, PCB_KERNEL_SP(tp)
  addi sp, sp, OFFSET_SIZE
  sd sp, PCB_KERNEL_SP(tp)
  addi sp, sp, -(OFFSET_SIZE)
  ld a0, OFFSET_REG_SSTATUS(sp)
  ld a1, OFFSET_REG_TP(sp)
  ld a2, OFFSET_REG_SEPC(sp)
  csrw CSR_SSTATUS, a0
  csrrw a0, CSR_SSCRATCH, a1
  csrrw a1, CSR_SEPC, a2
  ld ra, OFFSET_REG_RA(sp)    
  ld gp, OFFSET_REG_GP(sp)
  ld t0, OFFSET_REG_T0(sp)
  ld t1, OFFSET_REG_T1(sp)
  ld t2, OFFSET_REG_T2(sp)
  ld s0, OFFSET_REG_S0(sp)
  ld s1, OFFSET_REG_S1(sp)
  ld a0, OFFSET_REG_A0(sp)
  ld a1, OFFSET_REG_A1(sp)
  ld a2, OFFSET_REG_A2(sp)
  ld a3, OFFSET_REG_A3(sp)
  ld a4, OFFSET_REG_A4(sp)
  ld a5, OFFSET_REG_A5(sp)
  ld a6, OFFSET_REG_A6(sp)
  ld a7, OFFSET_REG_A7(sp)
  ld s2, OFFSET_REG_S2(sp)
  ld s3, OFFSET_REG_S3(sp)
  ld s4, OFFSET_REG_S4(sp)
  ld s5, OFFSET_REG_S5(sp)
  ld s6, OFFSET_REG_S6(sp)
  ld s7, OFFSET_REG_S7(sp)
  ld s8, OFFSET_REG_S8(sp)
  ld s9, OFFSET_REG_S9(sp)
  ld s10, OFFSET_REG_S10(sp)
  ld s11, OFFSET_REG_S11(sp)
  ld t3, OFFSET_REG_T3(sp)
  ld t4, OFFSET_REG_T4(sp)
  ld t5, OFFSET_REG_T5(sp)
  ld t6, OFFSET_REG_T6(sp)
  ld sp, OFFSET_REG_SP(sp)
.endm

ENTRY(enable_preempt)
  ld t1, current_running
  ld t0, PCB_PREEMPT_COUNT(t1)
  beq t0, zero, do_enable
  addi t0, t0, -1
  sd t0, PCB_PREEMPT_COUNT(t1)
  beq t0, zero, do_enable
  jr ra
do_enable:
  not t0, x0
  csrs CSR_SIE, t0
  jr ra
ENDPROC(enable_preempt)

ENTRY(disable_preempt)
  csrw CSR_SIE, zero
  ld t1, current_running
  ld t0, PCB_PREEMPT_COUNT(t1)
  addi t0, t0, 1
  sd t0, PCB_PREEMPT_COUNT(t1)
  jr ra
ENDPROC(disable_preempt)

ENTRY(enable_interrupt)
  li t0, SR_SIE
  li t1, SR_SUM
  or t0,t0,t1
  csrs CSR_SSTATUS, t0
  jr ra
ENDPROC(enable_interrupt)

ENTRY(disable_interrupt)
  li t0, SR_SIE
  li t1, SR_SUM
  or t0,t0,t1
  csrs CSR_SSTATUS, t0
  jr ra
ENDPROC(disable_interrupt)

ENTRY(ret_from_exception)
  /* TODO: */
  RESTORE_CONTEXT
  sret
ENDPROC(ret_from_exception)

ENTRY(exception_handler_entry)
  SAVE_CONTEXT

  csrw CSR_SSCRATCH, x0

  /* Load the global pointer */
  .option push
  .option norelax
  la gp, __global_pointer$
  .option pop

_lock_kernel:
  la  t1, kernel_lock
  li  t2, 1
  amoor.w t0, t2, (t1)
  bnez  t0, _lock_kernel
  /* TODO: load ret_from_exception into $ra
   * so that we can return to ret_from_exception
   * when interrupt_help complete.
   */
   la ra, ret_from_exception

  /* TODO: call interrupt_helper
   * note: don't forget to pass parameters for it.
   */
   mv a0, sp
   csrr a1, CSR_STVAL
   csrr a2, CSR_SCAUSE
   j interrupt_helper
ENDPROC(exception_handler_entry)
